the.com/gravity assist
stealing a planet's momentum to fling spacecraft across the solar system for free
momentum theftthe planet slows imperceptibly; you speed up enormously
voyager veteranused Jupiter and Saturn to escape the solar system
fuel savingssome missions impossible without these free velocity boosts
reverse gearworks to slow probes down toward the inner planets
chained slingshotsCassini used Venus, Earth, and Jupiter en route to Saturn